Roger,
Well, it seems to be even more complicated than that! The cargo net inserts were only supposed to come on the tufskin models, which were NOT supposed to have the FCS fin slots. The mast bolt inserts are apparently a hidden mast track with fixed nut positions.

It seems that I have a unique board. I have a sportech model with the mast track AND a full eva deck that looks exactly like a tufskin model. This was not what I ordered, but that's what came - even as a surprise to the dealer. It has the slot for the center board, the FCS fin slots in the back, and the cargo net inserts on the deck. I don't know if this was a transition design, or one-of-a-kind, or just a mistake. The dealer verified that it is indeed a sportech by sending the serial number to the US distributor.

I still haven't gotten my X-186 down yet to check the footstraps.
Brian